Just under 70% of African-American children surveyed said they had no or low ability to swim. Low ability merely meant they were able to splash around in the shallow end. A further 12% said they could swim but had "taught themselves".

The study found 58% of Hispanic children had no or low swimming ability. For white children, the figure was only 42%.

"It is an epidemic that is almost going unnoticed," says Sue Anderson, director of programmes and services at USA Swimming.

The swimming body would like all children to be taught to swim.

Parents' responsibility

"We would like it to be like seatbelts and bicycle helmets," says Ms Anderson.

But the situation in the US can vary hugely even within a single state.

Unlike the UK, where learning to swim is enshrined in the national curriculum except in Scotland, the ultimate responsibility in the US often lies with parents.

"I would love to make it a rule like they have in the UK," says Cullen Jones, a gold medallist in the freestyle 100m relay in Beijing, and a spokesman for USA Swimming's Make a Splash campaign.

"It isn't a requirement, it isn't a priority in the US."

Jones's mother took him to swimming lessons after he nearly drowned at a theme park aged five. By eight he was swimming competitively.

The Make a Splash campaign is targeting all non-swimmers and their parents but there is a particular focus on ethnic minority families.

Fear factor

Many black parents are not teaching their children to swim.

Some might assume the fundamental reasons would be lack of money for swimming lessons or living in areas where there were no pools, but the reality is more complex.

"Fear of drowning or fear of injury was really the major variable," says Prof Carol Irwin, a sociologist from the University of Memphis, who led the study for USA Swimming.

Swimming never became a part of African- American recreational cultureProf Jeff Wiltse, Author, Contested Waters

Typically, those children who could not swim also had parents who could not swim.

"Parents who don't know how to swim are very likely to pass on not knowing how to swim to their children," says Ms Anderson.

In focus groups for the study, Prof Irwin said many black parents who could not swim evinced sentiments like: "My children are never going to learn to swim because I'm scared they would drown."

The parents' very fear of their children drowning was making that fate more likely.

The major reason behind the problem could lie in the era of segregation says Prof Jeff Wiltse, author of Contested Waters: A Social History of Swimming Pools in America.

"The history of discrimination… has contributed to the drowning and swimming rates," says Prof Wiltse.

In his work he identified two periods of a boom in swimming rates in the US - in the 1920s and 1930s when recreational swimming became popular and the 1950s and 1960s when the idea of swimming as a sport really took off.

Image caption
There are historical reasons why black children do not learn to swim

The first boom was marked by the construction of about 2,000 new municipal pools across the nation.

"Black Americans were largely and systematically denied access to those pools," he notes.

"Swimming never became a part of African- American recreational culture."

In the northern US that segregation in pools ended in the 1940s and early 1950s, but many white swimmers responded by abandoning the municipal pools and heading off to private clubs in the suburbs where segregation continued to be enforced.

"Municipal pools became a low public priority," he notes.

After the race riots of the 1960s, many cities did start building pools in predominantly black areas, says Prof Wiltse, but there was still a problem. Many of the new pools were small - often only 20 by 40ft (six by 12m) and 3.5ft (1m) deep.

Theories for low black American swimming rates

Propagation of incorrect scientific theories such as black people being much less buoyant

Historic factors going as far back as slaves not being allowed to learn to swim

Denial of access to pools in 1920s and 30s causing ripple effect to present day